Heat transfer unit



July 4, 1933. I w. R. CLARKE 1,916,656

HEAT TRANSFER UNIT File'd June 15, 1931 //v l/EN ax? QW FZ Patented July 4, .1933

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RADIATOR COMPANY, OF HABTFORECONNECTICUT, A CORPORATION 01? CONNECT-- Application filed June 15,

This invention relates to heat transfer units, more particularly heat radiators of the type described in United States Patent llo. 1,646,384, October 25, 1927, which comprise [M a central tubular metallic core with a plurality of fins of sheet metal whichprovide extendedradiating surfaces spaced thereon and held by the expansion of the tube outwardly.

against the edges of holesin the fins.

In the prior construction the expansion of the tube tended to stretch the holes in'the fins and distort the surrounding metal, particularly if the fins were made of 'lkthin or soft metal, so that the inner edg l of the fins would not be contacted squarely and flatly against the surface of the tube, that is, there would be linecontacts between the fins and the tube with the result that the heat as conducting paths from the tube to the fins would ,be reduced to a minimum causing a lowering of efiiciency, and the outer sections of the fins would be more or lesscupped or buckled so that they would look irregularly spaced and not parallel and at right angles t to the tube, thus detracting from the appearance of the unit. Thin fins if theired es are flatly and wholly engaged .and tight em-- bedded in the surface of the tube an they are not buckled or distorted by the process of securing them, not only ensure rapid radiation but allow more fins to be applied to the tube per unit of length, without detracting from the appearance. Furthermore if the fins cup when the tube is expanded they are U more or less resilient and their bite or hold against the tube is thus reduced, which is particularly the case if the inner edges of the fin are provided with flanges that lie'against 4 andextend along the tube.

near 'rnAusr-En. time:

1931. Serial .No. 544,479.

around the holes made to fit the exterior of the tube, are slightly offset from the outer areas, leaving the inner and outer areas parallel, which shaping stifiens the fins and provides means which allow a slight outward expansion of the inner areas when the tube is expanded, without distorting or cup ing the entire fins or throwing the inner edges out so that they will not embed flatly in the metal of the tube.

In the accompanying drawing Fig. 1

shows a side view of a radiator section con structed in accordance with this improvement. Fig. 2 shows-a face view of the same. Fig. 3 is a longitudinal section showing only a few of the fins on the tube. Fig. 4 is a detail with the thickness of the metal greatly increased in order to illustrate the manner in which the fins contact with the tube.

The unit shown has a central tubular core 1 which is commonly made of copper or 'snmlar good heat conducting metal, of the required thickness, diameter and length. The fins 2 desirably copper or other suitable metal may be of any approved size and outline. The fins are stampedto shape from thin sheet metal with a central perforation 3 which has substantially the same diameter as the original outer diameter of the tube upon which the fins are to be placed. Preferabl at the same time that the fins are stampe to shape circular areas 4 surrounding the perforations are offset from the'lar er outer areas 5. The offset areas are dis aced but slightly, are small, and they remain parallel with relation to the outer areas.

- Offsetting fins of thin sheet metal in this manner 'stiflens them as a whole. After these ofiset fins have been placed on the tube and held at the specified distances apart the tube is expanded from the interior according to the disclosure in the patent above referred to.

On fins of this shape the outward strains resulting from the expansion of the tube are resisted and absorbed by the-restricted stifl ofiset areas which surround the-tube so that the outer areas of .thefins are not buckled or distorted. Such flexing or distortion of the metal of the fins as occurs place at the angular junction 6 between the small inner areas 4 and the large outer areas 5, as is roughly indicated to an exaggerated degree in Fig. 4. This leaves the outer areas of the fins smooth and parallel with each other without any substantial obstruction to the flow of air between and against the surfaces of the fins, and the inner areas as well as the outer areas extending in planes at right angles to the surface of the tube with the inner edges 7 of the inner areas flatly and fully binding against and very slightly em bedded in the surface of the metal of the tube, so that the conductivity of the joint will have maximum efficiency and will be suificiently tight to remain so. Such expansion of the tube as occurs in use is transmitted through the small ofi'set inner areas to and expended at the angular junction between the inner and outer areas. Any desired number of these fins may be threaded on the tubes and any number of units may be assembled with the required piping to produce the predetermined radiation.

The invention claimed is:

1. A radiator unit comprising a metallic tubular core, and ,a plurality of thin sheet metal fins with central perforations located upon said core, said fins having inner areas that are oflset from but are parallel with the outer areas, both said inner and outer areas extending at right angles to the axis of the tubular 'core with the thin inner edges of the inner areas in close contact with and embedded in the exterior surface of the tubular core perpendicular thereto.

2. A radiator unit comprising a metallic tubular core, and a plurality of thin sheet metal fins with central perforations the thin edges of which are closely engaged with and embedded in the core perpendicular thereto, said fins having small inner annular areas surrounding the perforations and large outer areas ofl'set from the inner areas, said areas extending parallel with each other and at right angles to the axis of the tubular core and connected by sections designed to yield under stress due to expansion of the tubular core.

WALTER R. CLARKE. 

